This invention relates to a tip brake mechanism for a wind generator blade and more particularly to a tip brake mechanism which is designed to rotate the tip of a wind generator blade so as to slow the rotation of the rotor when a malfunction occurs in the other features of the machine which are designed to keep the rotor at a uniform speed.
Wind generators are normally comprised of a bladed rotor shaft which is connected to a gear box which in turn is connected to a generator. A mechanical brake assembly is also normally provided for preventing the blade from rotating during periods of non-use and for stopping the machine if there is a grid failure or other failure which which would allow the rotor to free wheel or go into overspeed. The mechanical braking system for the wind generator will also occasionally malfunction and the tips must deploy to keep the generator from going into overspeed.
One type of prior art braking device causes the tip of the blade to be rotated about its longitudinal axis, relative to the remainder of the blade so as to slow the rotation of the blade. In the AeroStar mechanism, a spring which is loaded to approximately 1200 pounds pressure serves as the governor. Thus, in the AeroStar mechanism, approximately 1200 pounds of centrifugal force must be exerted on the tip for the brake mechanism to deploy. Consequentially, once deployed, the 1200 pound spring pressure is attempting to reset the tip and does so once the blades have slowed sufficiently to overcome the combined aerodynamic and centrifugal forces which are keeping them deployed. Unfortunately this sends the machine back into overspeed and the cycle repeats. This creates quite a destructive situation on the blades and the tip mechanism as they may cycle in and out for many hours.
The AeroStar mechanism is undampened and each tip deployment and reset imposes severe shock loads upon the entire blade and machine structure. This requires additional structural material to be used in manufacture of the blades to handle the extreme loads.
Further, the AeroStar tip mechanism is also heavy and the weight is distributed toward the tip, which also increases the blade structural material necessary to adequately carry the load of normal operation.
The AeroStar tip mechanism is bulky and must be serviced from a hole in the end of the blade tip. The new airfoils designed for wind turbines are thinner and do not have the internal space to house the AeroStar tip mechanism.
It is therefore a principal object of the invention to provide an improved tip brake mechanism for a wind generator blade.
A further object of the invention is to provide a tip brake mechanism for a wind generator blade which causes the tip to be deployed when subjected to approximately 1200 pounds of centrifugal force but which will not be reset until the centrifugal force drops to approximately 200 pounds.
A further object of the invention is to provide a tip brake mechanism for a wind generator blade wherein the trigger and the reset mechanism are separately controlled.
Still another object of the invention is to provide a tip brake mechanism for a wind generator blade which reduces the shock loads to both blade and turbine associated with overspeed tip deployment and reset.
Yet another object of the invention is to provide a tip brake mechanism for a wind generator blade which is lighter than the prior art devices.
Still another object of the invention is to provide a tip brake mechanism for a wind generator blade which is mounted relatively close to the blade root thereby permitting the utilization of a lighter tip.
Still another object of the invention is to provide a tip brake mechanism for a wind generator blade which enables the blade to be constructed with less structural materials.
Still another object of the invention is to provide a tip brake mechanism where in the blade tips are easily removable for repair, maintenance or exchange.
Yet another object of the invention is to provide a tip brake mechanism for a wind generator blade wherein a majority of the mechanism is easily replaceable.
Still another object of the invention is to provide a tip brake mechanism for a wind generator blade which is economical of manufacture, durable in use and refined in appearance.
These and other objects of the present invention will be apparent to those skilled in the art.